Oscillatory conditions significantly affect the thermal-hydraulic characteristics of floating reactors, leading to changes in the growth of chalk river unidentified deposit (CRUD).

This study aims to investigates CRUD growth on fuel rod bundles under oscillatory conditions.

Firstly, based on the data exchange method, the one-dimensional system program RELAP5 and the CFD (Computational Fluid Dynamics) program ANSYS Fluent were coupled to simulate the primary loop, and mathematical models of coolant flow and corrosion product deposition growth under oscillatory conditions were added to the simulation. Then, CRUD growth calculations and coolant flow mathematical models under oscillatory conditions were embedded into the multiscale simulation. Finally, the influences of oscillatory conditions on flow characteristics in rod bundle channels, fuel rod wall temperature, and CRUD growth were analyzed.

The simulation outcomes reveal that oscillation induces periodic variations in both the coolant flow rate and outer wall temperature of the rods. At lower axial heights, CRUD grows thicker on the rods near the peripheral wall. At higher axial heights, the CRUD distribution pattern tends to be consistent across all rods. The CRUD thickness distribution in the circumferential direction of the fuel rods tends to form an elliptical pattern in polar coordinates.

Fluctuations in flow rate and temperature can enhance erosion in the tangential direction of oscillation, diminish the deposition process, and result in varied CRUD distribution patterns at distinct positions.